Hi Mark,
sorry, Covid-19 slows down processes here and messes everything up :-(
I have uploaded my test source codes. I have compiled a 64-bit installation which initializes the 64-bit WebUpdate process. I have re-compiled the original WebUpdate client as x64. All files are in the ZIP.
http://www.lindersoft.com/projects/WebUpdate_x64.zip
Just for fun, please install WebUpdate_x64.exe (my x64 test installer) and after the installation, run WUPDATE_SSL.exe unter c:\program files\WebUpdate_x64. It detects the 64-bit configuration details.
Does this work on your machine?
Sorry again for the delay.
Friedrich